Oxidation of nonaromatic organic compounds



2,695,313 Patented Nov. 23, 1954 OXIDATION OF NONAROMATIC ORGANIC COB/[POUNDS William G. Toland, Jr., San Rafael, Califi, assig'nor to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application December 28, 1951, Serial No. 263,954

Claims. (Cl. 260-530) This invention relates to the oxidation of organic compounds; more particularly, it relates to the oxidation of non-aromatic organic compounds containing acid pre cursor groups.

This application is a continuation-in-part of my application Serial No. 168,850, filed June 17, 1950, now Patent No. 2,587,666. That application described a process for oxidizing oxygen-containing products of the partial oxidation of alkyl aromatic hydrocarbons through the use of a new oxidizing agent, i. e., a mixture of elemental sulfur and aqueous alkali. In that application the oxidation of toluic acids to phthalic acids with elemental sulfur and aqueous sodium hydroxide at 600 F. was described in detail. The oxidation of other aromatic organic compounds such as acetophenone, benzyl alcohol, ethyl benzoic acid, and the like, were also described. The alkyl aromatic hydrocarbons themselves may be converted to aromatic carboxylic acids by the process of the invention, but the yields are very much lower than those obtained when a partially oxidized charging stock is treated. It is believed that the reaction proceeds more readily with the partially oxidized derivatives of alkyl aromatic hydrocarbons because they are substantially more soluble in water and in aqueous alkaline solutions than are the hydrocarbons themselves. Indications are that higher yields of aromatic carboxylic acids may be obtained from the hydrocarbons if the reaction mixture is subjected to extremely violent agitation during the reac tion period.

It has now been found that this oxidizing agent may be effectively employed to oxidize non-aromatic organic compounds which contain oxygen in an acid precursor group.

Thus, aliphatic alcohols, aliphatic aldehydes, aliphatic ketones, esters formed from aliphatic acids and aliphatic alcohols, and ethers formed from aliphatic alcohols, may readily be oxidized to aliphatic'carboxylic acid derivatives. Pursuant to the invention, a non-aromatic organic compound containing an acid precursor group is oxidized to produce aliphatic carboxylic acids and aliphatic carboxylic acid salts by contacting the organic compound with sulfur and an aqueous solution of a basic material selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides at temperatures ranging from 300 F. to the critical temperature of water and under a superatmospheric pressure sutficieut to maintain a part of the water in liquid phase.

The invention will be understood upon consideration of the following examples:

Example 1 148 g. of normal butanol, 256 g. of sulfur, 100 g. of sodium hydroxide and 1500 cc. of water were charged to 4 /2 liter autoclave. The autoclave was heated to 550 F. and maintained at this temperature for 2 hours, during which time the autoclave was continuously shaken. The pressure in the autoclave rose to 2200 p. s. i. g. during the reaction period. The autoclave was cooled and the gaseous products were bled from the autoclave through a caustic solution. The caustic gained 140 g. in weight during the contact with the reaction gases. The liquidv products of the reaction which had a reddish color were removed from the autoclave and steam stripped. From the overhead 45.5 g. of normal butanol were recovered. During the reaction 1.4 moles of normal butanol were consumed. The stripped liquid product was acidified with sulfuric acid which caused evolution of carbon dioxide and hydrogen sulfide. The acidified solution had a strong odor of acetic acid. Sulfuric acid was added until the pH of the liquid was lowered to a value of 2. The products were then extracted with three 100 cc. portions of 5 diethyl ether. The ether was evaporated from the extract phase, leaving a residue of 25.6 g. of liquid which was fractionated in a column packed with glass helices. The following cuts were obtained:

Vapor tempera- Grams N. E. ture, 0.

acetic and pro- Yield, molar percent aliphatic acids Conversion,

Temperature, F. rcent Example 2 232 g. of acetone, 160 g. of sulfur, 200 g. of sodium hydroxide, and 1800 cc. of water were charged to a 4 /2 liter autoclave. The mixture was heated to 350 F. for 2 hours, during which time the pressure was held constant at 250 p. s. i. g. The liquid products were steam stripped and 16.5 g. of an organic layer were recovered overhead. The residual water layer was acidified to pH 2 with sulfuric acid. The acidified product was filtered and 61.7 g. of a dark red-brown cake were obtained. The cake was neutral. The pH of the filtrate was adjusted to a value of 7 and the filtrate was evaporated to reduce its volume and then extracted with ether. No residue was found in the ether extract. The filtrate was then acidified to pH 2 and extracted with ether. The ether was evaporated, leaving 26.1 g. of residue. The residue was distilled in a column packed with glass helices. The follow- 0 ing cuts were obtained:

Vapor Out No. tempera Grams Ce. N. E

ture, O. 65

The major product thus appears to be acetic acid.

Example 3 Example 2 was repeated with the exception that 4 moles of acetaldehyde were substituted for the acetone. The principal product was again found to be acetic acid.

The oxidation reactions above described proceed with the consumption of both elemental sulfur and water. Sulfur appears to be the effective oxidizing agent and 1s reduced to hydrogen sulfide which may be recovered and converted" to sulfur for further use. The oxygen of the carboxyl groups comes from the water.- While only sulfur and water appear to be consumed during the oxidation of the charging stocks, it has been found necessary to have substantial'amounts-of a basic materialsuchas an alkali metal hydroxide or an alkaline earth"; metal-hydroxide present in the reaction mixture. The -role:of tlie basic material has not been definitely establishedpbut'it appears to function as a solvent for both the: charging. stock and the sulfur, and intermediate reactions may occur" in-awhich the basic material participates without' being consumed.

Inaddition to the. aliphatic alcohols, aldehydes and ketones which are oxidized by the process of the invention in thermanner specifically exemplified above;.various intermediately oxidizedaliphatic hydrocarbons may be converted toaliphatic carboxylic acid derivatives by the" process ofthe invention, thuscli-ethyl ether is oxidized:

to aceticacid and ethyl acetate isoxidized to acetic acid. Not only are oxygenated; aliphatic hydrocarbons con taining acid'precursor groups such as the alcohols, the: aldehydes and the ketones oxidized to acids by the process" ofthis invention, but otheraliphatic hydrocarbon deriva-- tives such as the aliphatic amines and nitroaliphatic compounds are attacked by the aqueous alkali at reaction temperature to yield acidprecursor.containingproducts which are then oxidized to acids by the aqueous caustic and sulfur.

Sulfur can be introduced into the reaction mixture as. such, or in the form of a water-soluble polysulfide, as shownin the above examples, or in the form of a sulfur compound which is convertible to sulfur under the conditions of the reaction. For example, hydrogen sulfide and sulfur dioxide may be introduced into the reaction mixture in lieu of sulfur and acomparable reactionis ob.- tained. Sulfur dioxide or a water-soluble sulfite may be employed in the reaction mixture as the primary source of sulfur for the oxidation. When these materials are used, a small amount of elemental sulfur, not usually exceeding-about 6% of'the amount which would be required if,elemental sulfur were to be used as the sole oxidizing agent, may be introduced into the reaction mixture. This. small amount of sulfur initiates the oxidation reaction and some hydrogen sulfide. isv formed. Thehydrogen sulfide. then reacts Wit h sulfur. dioxide. to. produce. more. sulfur and the reaction (continuesin this manner. The sulfur may also be introduced into the reaction mixture in the form of thionic acids and their salts, or sodium-thiosulfate may be employed as the source of sulfur. These materials decompose under the conditions of the reaction to produce sulfate, sulfite, and sulfur, and the sulfite and sulfur are consumed in the oxidation reaction. In general, any inorganic sulfur compound containing atleast one sulfur atom which is at a valence level below plus 6 and above minus 2 may be introduced intothe reaction mixture as the primary source of sulfur and where such materials are used a small amount of elemental sulfur is desirably but not necessarily introduced'into the reaction mixture to act as a catalyst'or initiator.

While sulfur acts as the oxidizing 'agent'inthe reaction, the oxygen necessary'to form the carboxyl groups-of the acidic reaction product is supplied by water; consequently, water mustbe present in the reaction mixture: It is dcsirably present in amounts greatly exceeding the amount theoretically required to supply the necessary oxygen.

The amount of sulfur which'is desirably present in the reaction mixture may be determined from a balanced equation for the oxidation reaction in which sulfur acts as the oxidizing agent and Water suppliesthe oxygen to' the carboxyl groups: which are formed. For example, ethyl alcohol isoxidized pursuant to the following equa- Accordingly, two moles of sulfur and a mole of water are required. to oxidize each mole of ethyl alcohol.

As indicated in Example 1, the acid produced may not contain the same number-of carbon atoms as does the organic material subjected to. oxidation. Apart of the carbon chain may be consumed in the oxidation and when this occurs it is converted to carbon dioxide. Where carbon dioxide is produced in this manner, additional sulfur must be employed if high conversions of the feed are desired.

The basic materials suitable for use in theprocess of this invention include, in addition to the sodium hydroxide illustrated above, the other alkali metal hydroxides, especially potassiumhydroxide; and the" alkalineearth metal hydroxides, especiallymagnesium hydroxide, calcium hydroxide and barium hydroxide; also, their salts with weak inorganic acids as carbonates, bicarbonates, sulfides, and sulfites. Tl'leamount of the basic material which is present in the reaction mixture may bevaried over a considerable range. At least sufli'cient basic material to react with all'of thecarboxyl groups formed in the course of thereactionto form the metal saltsof the acids should be present. The basic material .is preferably present somewhat in' excess of this. amount; larger amounts of basic material, for'example, five to six times the amount necessary to: neutralize. the carboxylic: acids formed, have been employed with good effect. The basic material may be entirely in solution in water or it may be employed in the-form; of. a. dispersion or slurry. The moderately soluble alkaline earth metal hydroxides are suitably introduced into: the-reactor in the form of' an aqueous slurry.

The. reaction should be conducted" at temperatures above about 300 F. At lower temperatures: the reac-'- tiorris very slow. Themaximum temperature of' reaction'should be below the:critialitemperature' of water in order that a liquid: aqueousphase may. bepresent in the reaction'mixture. Preferably; thereaction is conat temperatures-inthe'range from 325 FLto Fressure is a dependentvariablein thereaction. lf'a. batch type operation is'conductedin'a closed containeror bomb, the autogeneous pressureiwill he sumcient to maintain a partofthe water'in liquid phase. Ordinarily, the pressure during-the reaction is in the; range. of 250 to 3000 p; s. i. g.

The recovery of the'acid'product from the reaction mixture wasdescribedin Example -1 above. Theipurification' procedure may be variediconsiderably, buttthe: est sential steps are liberatingztheorganicacids. by acidifying the reaction product with a strong. mineral acid and separating :therfree. organic acid? by fractional distillationor. extraction.

Iclaim:

l. A: process for" oxidizing. a non-aromatic organic compound fcontainin'g :oxygen intan acid precursor: group, which; comprises: contacting: the organic: compound with 1' water, sulfur. and a-basic material selectedtfromthe group= consisting of alkali metal hydroxides and theirsalts-with. weak inorganicacidsiandalkaline earth metal hydroxides and their salts with :wcakiriorganicacids at a temperature from 300 F. to the. criticaltemp'erature of water-and under a superatmospheric pressure sufficient to maintain part of the; Water in liquid. phase.

2. A processfortoxidizingiarr organiccompound'of the group consistingofi aliphatic alcohols,.aliphatic ketonest andalphatic. aldehydes; which" comprises: contacting the" organic compound with water; sulfur and a basic material selected from the? group. consisting: of alkali metal hy-'- droxides and alkaline earth metal hydroxides at a'temperature inrthe range'from 325 F. to 600 F. andiunder a superatmospheric pressure sufficientto maintain a part of the water in .liquid phase.

3. Amethod as defined in claim 2, wherein-the organic"- compound is"an aliphatic? alcohol.

4. The method as definedin claim 2, wherein'the or-' ganic compound .is an aliphatic ketone.

5: Themethod" asdefined in claim 2, wherein theorganic compound is an aliphatic aldehyde;

References Citedin'thefile of this patent Beard et al., J. Chem; Soc. (London), vol. 1944, pp. 4 and 5.

AdamsetaL, Org.. Reactions, vol. III (1946), pp. 84-9 2. 

1. A PROCESS FOR OXIDIZING A NON-AROMATIC ORGANIC COMPOUND CONTAINING OXYGEN IN AN ACID PRECURSOR GROUP, WHICH COMPRISES CONTACTING THE ORGANIC COMPOUND WITH WATER, SULFUR AND A BASIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL HYDROXIDES AND THEIR SALTS WITH WEAK INORGANIC ACIDS AND ALKALINE EARTH METAL HYDROXIDES AND THEIR SALTS WITH WEAK INORGANIC ACIDS AT A TEMPERATURE FROM 300* F. TO THE CRITICAL TEMPERATURE OF WATER AND UNDER A SUPERATMOSPHERIC PRESSURE SUFFICIENT TO MAINTAIN PART OF THE WATER IN LIQUID PHASE. 